This invention concerns attaching drive motors to engine cooling fan systems.
Such systems include a fan attached to a motor which is in turn attached to the motor mount of a fan housing which holds it in place and positions the motor/fan assembly to operate with a heat exchanger. The attachment of the motor to the motor mounting structure is subject to a number of considerations. For servicing, the attachment should be capable of easy assembly and disassembly, e.g. with hand tools. It must also undergo many hours of exposure to vibration and temperature cycling without developing looseness or rattling between the motor and motor mounting structure. Additionally, the attachment should function despite manufacturing variances inherent in mass-produced parts.
Many existing attachment systems use metal fasteners such as screws, studs, nuts, and rivets in order to satisfy these requirements. These fasteners add cost to the product and increase part count. In a market where demands on quality are increasing, they may also introduce additional failure modes, some of which are difficult to detect. Measures typically are taken to insure that parts are not shipped with fasteners which are missing, incorrectly selected, or incorrectly tightened. Finally, these fasteners must be supplied with replacement parts, to insure the integrity of repairs.
We have discovered a motor mount assemblyxe2x80x94particularly for vehicular engine-cooling fan motorsxe2x80x94which allows a motor to be mounted into and retained by a motor mounting structure without additional fasteners which can withstand the rigorous requirements to which vehicular motor mounting systems are subjected.
One aspect of the invention features an assembly in which the motor includes multiple connector elements (such as tabs), which are integral with the motor. The motor mount is integral with at least a portion of the fan housing, and the mount includes multiple recesses which are sized and shaped to receive and engage the connector elements of the motor by combined axial and rotational movement of the motor relative to the motor mount. In some cases, the connector elements are radially-extending tabs, and the motor-mounting recesses of the housing are sized, shaped and positioned to receive the tabs as a bayonet mount. Alternatively, the connector elements of the motor may include screw threads which cooperate with the motor-mounting recesses to form a screw mount.
Preferably, the motor-mount also includes radially elastic supports which cradle the motor so as to exert a radial force on the motor. The motor is rotatable and axially moveable relative to the radially elastic supports, for ease of assembly. Another feature of the invention may include multiple rigid elements (e.g. rigid ribs) positioned to limit the radial travel of the motor. The rigid elements (or at least one of them) may be different from or integral with the radially elastic supports. In one embodiment where they are integral with the radially elastic supports, the radially elastic support includes, at least in part, surfaces which extend in a generally circumferential direction from a rigid rib and contact the external surface of the motor at a position slightly inward of the innermost rib portion, forming an interference fit.
The fan housing generally includes members (e.g. stators or arms) which extend generally radially inward and support the motor-mount. Often the housing includes a structure which surrounds the fan, controls air recirculation, and supports the radially extending members that in turn support the motor mounts. It is also common for the housing to include an air guide structure to guide the airflow between a heat exchanger and the fan. Typically, the motor mount and/or the radial mount supports, and/or the structure extending around the fan and/or the air-guide structure are injection-molded plastic, most typically as a single part.
The connector elements of the motor are typically metal. The connector elements may be integral with the motor flux ring, the motor case, or end-cover.
The connectors (e.g., tabs) may be of different dimensions with the motor mount recesses sized and shaped to key the orientation of the motor as it is inserted into the motor mount. Another way to orient the motor is to use tabs and motor-mount recesses which are spaced unevenly around the circumference of the motor.
One or more resilient latches on the motor mount can prevent the motor from rotating after it is rotated into position. Preferably, the connector elements and the motor mount recesses are shaped to permit insertion by rotation in the direction of torque that the operating fan exerts on the motor.
The motor mount recesses may be sized and shaped to permit the motor to slide into the motor mount as the motor is mounted from the front (i.e. the fan side of the motor mount). In this case, the motor-mount structure may include a heat or splash shield. Alternatively, the motor mount recesses may be sized and shaped to permit the motor to be mounted from the rear. In this case, the motor mount will generally include an opening through which the front of the motor will project when the motor is in position.
The invention also features methods of assembling the above described motor/fan assembly by sliding the motor axially into the mount and twisting it to secure the integral motor connectors in the motor mount.
Another aspect of the invention features an assembly in which the motor-mount comprises at least one resilient latch which deflects upon axial insertion of the motor and, after insertion, moves to a position in which the latch limits motor travel. The motor includes at least one feature which cooperates with the latch. In effect, a spring lock serves to lock the motor in position.
Many of the preferred features described above may also be used on this second aspect of the invention: a) radially elastic supports which cradle the motor and exert a radial force on the motor, the motor being axially moveable relative to the elastic supports; b) multiple rigid elements (e.g. ribs) positioned to limit the radial travel of the motor, the rigid members in some cases being integral with the radially elastic supports; c) the use of a single injection molded plastic part for the various parts of the housing (motor mount, generally radial supports for the mount, a fan-surrounding shroud and/or air guide structure).
Preferably, the motor feature that cooperates with the latch may be a) the edge of, or a tab integral with, the motor""s flux ring; b) the edge of, or one or more tabs formed integrally with, the motor case; c) (where the motor includes an end cover which wraps around the edge of the motor case) the edge of the end cover; d) one or more tabs formed integrally with a motor end cover; and/or e) one or more holes in the motor case. These motor feature(s) may be configured to prevent rotation of the motor case. If the motor is mounted from the front, the motor-mounting structure may include a splash and heat shield. When the motor is mounted from the rear, the front portion of the motor may extend through an opening in the motor-mount structure.
To assemble the above-described second embodiment, the motor is inserted into the motor-mounting structure until it contacts axial stops. At this point, an axial latch has engaged a feature on the motor, completing the axial retention.
The bayonet mount, screw mount or the axially snapping arrangement provides ease of assembly. Cradling features may be needed to provide rigidity, durability, and robustness that satisfy manufacturing tolerances. For example, the flexible regions of these cradling features are sized to have an interference fit with the motor body over a range of manufacturing tolerances. They serve to maintain a tight fit between the motor and motor mounting structure over the range of dimensional variance inherent in production of both. Their flexibility also allows insertion of the motor with limited force, allowing manual assembly and disassembly for service. The stiff regions of these cradling features are sized to allow a small clearance between the motor and motor mounting structure over the range of dimensional variance. While they do not maintain a tight contact with the motor, they serve to limit movement of the motor within the motor mounting structure when the assembly is exposed to shock and vibration. This in turn limits strain on, and erosion of, the flexible regions of the cradling and the recesses in the motor mount described above.
The above-mentioned elasticity can alternately be accomplished through flexibility in the mounting structure rather than flexibility in specific cradling features.
The inner surfaces of the cradling features may need to have draft for easy injection molding. The motor mounting structure can be designed so that the cradling features rotate during insertion of the motor, so that the contacting surfaces become substantially parallel with the external contour of the motor. This rotation occurs circumferential twisting of pliable portions (e.g., the profile) of the motor mounting structure.
The features described above can be inverted, especially where the motor is fitted with molded plastic components. In this case, latches and flexible and rigid guiding features can be located on the motor assembly, wheras tabs, holes and other features to cooperate with said latches and guiding surfaces can be located on the motor mounting structure.